/Engine/Source/Runtime/Core/Public/ProfilingDebugging/CookStats.h
When you register a callback for reporting your stats, you will be given aTFunctionRefto call to add stats. This is the signature of the function you will call.
typedef [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< void(const [FString](API\Runtime\Core\Containers\FString) &StatName, const [TArray](API\Runtime\Core\Containers\TArray)< [StringKeyValue](API\Runtime\Core\ProfilingDebugging\FCookStatsManager\StringKeyValue) > &StatAttributes)> AddStatFuncRef